Optically inactive substance

Which of the following aldoses yields an optically inactive substance on reaction with sodium borohydride ... 

Dangschat and Fischer" have most elegantly extended the chemistry of the cyclitols by an investigation of the naturally occurring cyclitol, conduritol (XXIV). This optically inactive substance was discovered in... 

Dimethyl-l,l-cyclopentanedicarboxyIic acid can be prepared as a mixture of two optically inactive substances of different physical properties, NN and 00. When each is heated and, fhe reaction mixture worked up by fractional crystallization, NN yields a single product, PP, of formula C8H14O2, and OO yields two products, QQ and RR, both of formula QHi402. 

Oxidation of the methyl ether of vinyldihydromethylthebaol [xxiv, cf) = CI-I3] with potassium dichromate affords an ether-insoluble, yollow, optically inactive substance that may be a quinone [5]. A very small amount of phonanthrone togothor with a small quantity of an... 

That the adsorption of the cyclopentane ring seems to proceed mainly flatly in deuterium exchange on films has been stated above (see Section I,D). Of considerable interest are the investigations on asymmetric catalysis initiated by Schwab et al. (273). In their work, one of the optical isomers reacted a little faster than the other in a racemic mixture. Terent yev and Klabunovskii (274, 273) carried out the catalytic asymmetric synthesis from optically inactive substances. The reactions were accomplished on metals deposited on dextro- and levorotatory quartz. Organic optically active carriers and admixtures give a still greater effect. On this problem see Klabunovskii (276). At the present time still more active catalysts for the reaction of asymmetric hydrogenation and polymerization have been revealed (277-279). 

Anisotine (35) was obtained as a minor, optically inactive substance from Anisotes sessiliflorus C.B.Cl. (63) and also from Adhatoda vasica (65). The UV spectrum (Kmax 212, 226, 259, 301,312, and 356 nm) is very similar to that of 4(3//)-quinazolinone. It remained practically unaltered in acid or alkaline solution. The IR spectrum indicates the presence of an =NH, two carbonyl functions, and an aromatic carbomethoxy group. 

Example 6-3. Fluorochloromethane, CH2FCI. does not comprise an enantiomeric pair of substances it is a single optically inactive substance. Explain this fact by making a drawing of the molecule and indicating its plane of symmetry. 

Solution. The two enantiomeric molecules are the RR and SS forms of the formula given. The optically inactive substance is composed of RS or SR molecules, which are identical because of a mirror plane of symmetry bisecting the C—C bond. 

Allene has the structural formula H2C=C=CH2. Do all of the atoms lie in the same plane Would you predict that 1,3-difluoro-allene, HFC=C=CHF, exists as an enantiomeric pair of substances or as a single optically inactive substance ... 

The two circular-polarized beams of the incident radiation (I, levorotatory r, dextrorotatory) not only can be influenced with respect to their direction of rotation, but also, in the region of an absorption band, can be absorbed to a different extent by the sample, so that in addition to so-called optical rotatory dispersion (ORD), circular dichroism (CD) or the Cotton effect is observed [35] - (38J. Along with these classical methods of analysis, modem methods for the analytical investigation of surfaces and boundary layers have become very important, including the use of polarized light in ellipsometry ( Surface Analysis) and surface plasmon resonance. Under the influence of external forces (e.g., a magnetic field), even optically inactive substances can be caused to produce magnetooptic rotation. 

III. Classification of Methods of Producing Optically Active from Optically Inactive Substances... 

On the basis of the foregoing discussion, we can now attempt a new and full classification of the various methods—some old, some very recent —of producing optically active from optically inactive substances. We must consider in particular the allocation of asymmetric s3mthesis, in the sense defined by Marckwald, to its correct place in the scheme and we must also consider how many of the processes may operate in various biological syntheses and decompositions. 

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